The present invention relates to high purity abrasive particles comprising metal oxide for use in chemical-mechanical polishing compositions (or slurries). Polishing compositions or slurries used for chemical mechanical polishing (CMP) typically comprise an aqueous solution which contains abrasive particles, an oxidizing agent, a dispersant and/or a complexing agent. The abrasive particles are typically sub-micron in size.
U.S. Pat. No. 4,959,113 discloses an aqueous polishing composition containing alumina particles and aluminum nitrate that is added to the aqueous polishing composition to improve the polishing efficiency of the alumina particles.
This invention provides an aqueous polishing composition for polishing semiconductor substrates comprising submicron particles of a metal oxide and a soluble metal salt of the metal oxide. The soluble metal salt is present in a proportionate amount to adjust the aqueous concentration of metal ions to the equilibrium solubility of the metal oxide at the desired pH of the polishing composition thus providing an aqueous polishing composition having a stable pH.
Embodiments of the invention will now be described by way of example with reference to the accompanying drawings.